On Tue, Nov 28, 2017 at 11:24:35AM +0100, Maxime Ripard wrote: > Hi, > > Here is an attempt at transitioning away from the MMC raw environment to a > FAT-based one. Since the RFC was quite well received, I actually tested it > and fixed a few rough edges. > > You'll find the first RFC here for reference: > https://lists.denx.de/pipermail/u-boot/2017-October/310111.html > > And the second that originated in this series: > https://lists.denx.de/pipermail/u-boot/2017-November/311608.html > > The fundamental issue I'm trying to adress is that we've had for a > very long time the assumption that the main U-Boot binary wouldn't > exceed around 500 bytes. > > However, we're starting to get real close to that limit, and are > running out of silver bullets to deal with the consequences of having > a bigger U-Boot binary, the main consequence being that we would > have some overlap between the environment and U-Boot. > > One way to address this that has been suggested by Tom is to move away > from the raw MMC environment to a FAT-based one. This would allow us > to slowly migrate away, and eventually remove the MMC-raw option > entirely to reclaim that space for the binary. > > That cannot be done in a single release however, since we might have > environments in the wild already that people rely on. And since we > always encouraged people to use the raw MMC environment, noone would > expect that. > > This is even worse since some platforms are using the U-Boot > environment to deal with implement their upgrade mechanism, such as > mender.io, and force moving the environment would break any further > upgrade. > > The suggested implementation is to allow U-Boot to compile multiple > environments backend at once, based on the work done by Simon. The > default behaviour shouldn't change obviously. We can then piggy-back > on this to tweak on a per-board basis the environment lookup algorithm > to always favour the FAT-based environment and then fallback to the > MMC. It will allow us to migrate a raw-MMC user to a FAT based > solution as soon as they update their environment (assuming that there > is a bootable FAT partition in the system). > > This has just been compile tested on sunxi so far, and I'd like > general comments on the approach taken. Obviously, this will need to > work properly before being merged. > > Let me know what you think,
I think this is the right direction to head in. Can you please address the few outstanding points / questions and have something posted shortly after v2018.01 releases, and I'll apply it for inclusion in v2018.03? Thanks! -- Tom
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